1. Field of the Invention
The present invention relates to a process and a plant for building tyres. In greater detail, the invention concerns a method, a process and the equipment used for building the green tyre, to be subsequently submitted to a curing cycle for obtaining the final product.
2. Description of the Related Art
A tyre for vehicle wheels generally comprises a carcass structure including at least one carcass ply having respectively opposite end flaps in engagement with respective annular anchoring structures, integrated into the regions usually identified with the name of “beads”, and having an inner diameter substantially corresponding to a so-called “fitting diameter” of the tyre on a respective rim.
Associated with the carcass structure is a belt structure comprising one or more belt layers, disposed in radial superposed relationship relative to each other and to the carcass ply, and having textile or metallic reinforcing cords with a crossed orientation and/or substantially parallel to the circumferential extension direction of the tyre. At a position radially external to the belt structure, a tread band is applied which is of elastomeric material too, like other semifinished products constituting the tyre.
In addition, respective sidewalls of elastomeric material are applied at an axially external position to the side surfaces of the carcass structure, each extending from one of the side edges of the tread band until close to the respective annular anchoring structure to the beads. In tyres of the “tubeless” type, an airtight coating layer, usually named “liner” covers the inner surfaces of the tyre.
After building of the green tyre, carried out through assembly of respective components, a curing and molding treatment is generally carried out which aims at determining the structural stabilisation of the tyre by cross-linking of the elastomeric compounds, and impressing a desired tread pattern on the tyre as well as possible distinctive graphic marks at the tyre sidewalls.
EP 1 312 462 discloses a building system wherein along a production line there is a ply-feeding station, a carcass-building station, an assembling station and a belt-building station equipped with respective drums. Transport members movable along the production line carry out transfer of the workpieces from a work station to another, removing the workpiece from a drum for placing it on the drum of the following station.
EP 1 481 791 discloses a tyre production system comprising a plurality of carcass-building stations distributed to a given mutual distance for forming the carcass structures on respective carcass-building drums sequentially transferred along a carcass-building line. Along a belt-producing line the belt structures provided with tread band are formed on respective belt-building drums sequentially moved between belt-building stations to a predetermined distance from each other. The carcasses and belts are mutually assembled within a curing mold.
WO 2009/040594, in the name of the same Applicant, discloses a plant and a process for producing tyres, comprising the following steps: a) forming a carcass structure of a green tyre on a first building drum in at least one carcass-building line; b) forming a crown structure on an auxiliary drum in at least one crown structure-building line; c) shaping the carcass structure into a toroidal configuration for coupling it to the crown structure in at least one assembling and shaping station of the tyre being processed. Operation of the assembling and shaping station is synchronised with that of the carcass-building line and the crown structure-building line. Each carcass structure is maintained in engagement on the respective building drum at least until completion of the shaping step. The built tyre is cured and molded in a curing and molding line separated from the assembling and shaping station.